UFH in extensions – the low down

UFH extension

The benefits of warm water underfloor heating in the home are well established: improved comfort, no intrusion on wall or floor space and low running costs. But did you know that the advantages of underfloor heating can also be experienced in conservatories, extensions and single rooms by adding it to the existing heating circuit?

Where the structure is built (or upgraded) to meet current building regulations there will be sufficient insulation present to allow the UFH to work at low flow temperatures, so efficiency can be maximised and energy bills reduced.

There are two scenarios to consider:

Option 1 – a new-build with almost any floor structure

This is a really straightforward proposition; area packs, such as Nu-Heat’s OneZone®, are available for both screed and floating floors in various sizes up to 60m2. In areas larger than this or in two-storey extensions the system should be fully designed by an experienced supplier to ensure optimum performance.

Option 2 – an older extension with insulation but limited scope to increase floor height

In the past fitting UFH in older properties has been challenging, which is why Nu-Heat has developed the LoPro™ range.  Both LoPro™Max and LoPro™10 are low height profile systems which are laid easily over any existing floor.

LoPro™Max is perfect for renovation projects, offering the highest heat output of any retrofit UFH system.  The system uses a castellated panel to hold the pipe in place and this is then covered by a specialist self-levelling compound.  Due to its impressive heat performance, the OneZone pack is perfect for extensions with large amounts of glazing and also conservatories.

Another option, LoPro™10, is a composite gypsum construction with one-third less thermal mass than a screed floor, allowing it to heat up and cool down rapidly – making it more economical for retrofit properties and giving quick response times. Its low thermal resistance and high mass (15,5kg/m2) provide a high thermal output and solid feel underfoot.

System controls

A well-designed floor heating system maintains a comfortable floor temperature through accurately controlling the water temperature entering the floor. Water is taken from the existing heating system, passed through the control unit and then pumped directly to the underfloor heating tube. The floor temperature needs to be raised only a few degrees above the room temperature to maintain an effective comfort level.

There are generally two options for controlling the times at which warmth is available in the extension area:


Plumb into the existing radiator system and use the existing heating timer as the master control. The programmable thermostat supplied with the UFH will be able to call for heat in the room during the times set on the main timer, but not at other times. The room heating will switch off when the correct temperature is reached within these times. This is most effective when floor constructions with fast heat-up times are used.


Bypassing existing system controls to give independent control over the underfloor heating system. Ideally, independent control should always be the preferred option. However this is dependent on the location of the room in relation to the existing system.

Wireless programmable thermostats provide a major benefit when retrofitting UFH systems as they remove the need for potentially disruptive hard wiring.


UFH in screed can provide heating of up to 100 Watts per square metre of floor area. This is normally more than sufficient to provide room temperature without supplementary heating, however it is important to ensure that the heat output from the floor will meet the heat loss of the structure in extreme weather conditions, especially in highly glazed areas such as conservatories; the supplier should be able to confirm this. By appropriate programming of the controls, rooms with screed floors can be heated to match the radiator system.

Floating floors, LoPro™10 and LoPro™Max also offer good heat outputs and they warm up and cool down quickly, meaning the UFH can be operated with timings similar to those of a radiator system.

Floor coverings

There are very few restrictions on the type of floor covering that is suitable for use with UFH as long as some simple guidelines are followed. The choice of floor covering will impact on the eventual height build-up, and must be taken into account in projects with limited height availability.

Ceramic tile, stone and marble all conduct heat extremely well and can be laid as normal with a de-coupling layer and flexible adhesive. Engineered timber boards can either be floated or fixed in place depending on the sub-floor structure. Carpet with underlay can also be used as long as the tog value doesn’t exceed 2.5.

Benefits of UFH in an extension

  • High levels of customer satisfaction
  • Energy efficiency
  • No impact on wall space or interior design
  • Versatile – can be used on ground and first-floors
  • Low-height options available
  • Integration with existing radiator system & controls
  • Easy to install

Retrofitting UFH – what every installer needs to know

Over recent years the cost of heating has gone up dramatically meaning UK residents are increasingly carrying out insulation upgrades to reduce bills. Often linked to this type of major refurbishment is the need to upgrade the heat source – and this is where you come in, as it offers the perfect opportunity for you to promote underfloor heating (UFH) to the existing property market in place of radiators.


What makes a system fit for purpose?

The most important aspects of any heating product from an installer’s point of view are likely to be ease-of-use, robustness, reliability and heat output capability – in a retrofit situation the overall height build-up may also be important. A UFH floor construction that delivers on these critical aspects is what all installers are looking for.

The choice of heat source depends on the fuel supply – if gas is available a modern condensing boiler will work very efficiently with UFH as the low flow temperatures allow it to run in condensing mode for more of its operating time, making it the most economical choice. Alternatively, oil, lpg or any source that can deliver controlled heat at the required temperature can also be used. There can be situations where a heat pump will be a viable option, usually where the property is undergoing major renovation to bring insulation into line with current building regulations, especially where direct-electric heating is being replaced. The flow temperatures required must be low enough to allow it to operate efficiently and deliver a sensible CoP, so it is always worth checking with the system supplier.

Good system design is crucial to the success of any heating system, particularly UFH in a retrofit project. Before you start…


  • Get heat loss calculations done, as this will determine whether the system shall perform as required.
  • Upgrade insulation; typically this would include double-glazing, loft insulation and cavity or solid-wall insulation.
  • Investigate the Government’s Green Deal funding initiative as some of the upfront costs of insulation upgrades and UFH could be offset against future energy savings.

 Step-by-step – the easiest way to install Nu-Heat’s LoPro10® retrofit UFH


  1. Clear the floor area, repair and level the floor as required using self-leveling compound or replace/screw down uneven suspended timber floors.
  2. Lay pre-routed panel and castellated panel for pipe run back to manifold following the system design drawing supplied.
  3. Lay ‘pipe run’ panel where shown on the design drawing. This panel gives plenty of flexibility to install multiple pipes back to the manifold.
  4. Run 10mm pipe from the manifold to each designed zone.
  5. Fill and pressure test the system. This is a crucial part of any UFH installation as it ensures the system is watertight before final floor finishes are laid.
  6. Lay self-leveling compound to cover edge ‘pipe run’ panel and leave to dry for 24hrs.




  • Carry out all 1st fix mechanical pipework and electrical wiring, building and plastering work before installing retrofit UFH, which should be fitted at 2nd fix stage to avoid damage to pipes or panels – this floor construction can almost be considered in the same way as a floor finish.
  • Ensure the panel has a firm base on which to sit to remove any possibility of movement.
  • Pay particular attention to which end of the room will have turns panels; the other end will have straight panels butted up to the ‘pipe run’ panel.
  • Check which coil lengths go in each zone as they may vary in length and only trim each one to the length shown on the system design when all the coils have been installed.
  • Use the edge batten and the 15mm height of the panel to achieve an even, level finish for the self-leveling compound.


Final floor finishes

Tiles, engineered timber, carpet and vinyl are all suitable for use with retrofit so long as the supplier’s guidance on best practice is followed.

  • Tiles – a de-coupling membrane and flexible adhesive should be used to guarantee performance.
  • Engineered timber is recommended instead of solid hardwood flooring, as its structure is inherently stable. Glue, butt joint and free float the floor over the panel. A 5mm acoustic layer can be fitted under the panel on suspended timber floors if required.
  • Carpet plus an underlay suitable for UFH with a combined maximum tog value of 2.5 is recommended.



Customer satisfaction

Due to its good response times, a retrofit system such as LoPro®10 can be set up, controlled and run in the same way as a standard radiator system with similar system times and control settings. This means that homeowners do not have to radically change the way they use or program their heating system.

Warm houses, happy customers and a new market to make the most of in these trying economic times – retrofit UFH has got to be worth investigating.


Nu-Heat’s LoPro10™ retrofit UFH system has been designed as an alternative method of heating existing domestic properties. Homes built within the last 20 years and those that have undergone fairly standard insulation upgrades can now benefit from all the advantages of underfloor heating usually reserved for new-build.

LoPro10™ provides a practical, economical alternative to a traditional radiator-based system and is designed for use with existing or new gas/oil/lpg condensing boilers. A LoPro10™ system typically requires a flow temperature of 45˚C–55˚C – much lower than a typical radiator system which would have a flow temperature of 70˚C– 80˚C and complementing the performance characteristics of condensing boilers perfectly.


1. 1st & 2nd fix work – Before installing the LoPro10™ system, carefully plan the installation sequence. Carry out any building work plus 1st-fix plumbing and electrical work. Clean the site and repair/level floors. LoPro10™ is a 2nd-fix product.

2. A clear site – To avoid damage and provide a clean working environment, where possible the site should be free of other tradespeople when installing the LoPro10™ panels, castellated pipe tray and self-levelling compound.

3. Floor preparation – Floor preparation/repair is essential for a trouble-free installation. Before laying any LoPro10™ panels the floor should be made flat/ level. Where necessary use an appropriate self-levelling compound to achieve this. Suspended timber and floating floors should be repaired so that they are flat and capable of providing sound load-bearing support.

4. Floor finishes – Always ensure you use the laying/fixing method for the LoPro10™ panels that is appropriate for both the sub-base and the chosen final floor finish. Check the manufacturer’s recommendations for fitting final floor finishes in addition to those included in the Nu-Heat LoPro10™Installation Manual.

5. CAD design – Always review the CAD tube layout drawings supplied with the system; the floor areas covered by LoPro10™ panel and those covered by the castellated pipe tray are clearly indicated. Mark the areas out on the floor and double-check that the measurements match those on the CAD drawing. Any major anomalies should be discussed with the Nu-Heat system designer.

6. Edge battens – The edge batten placed around the perimeter of the room next to the castellated pipe tray can be used to determine the correct height for the self-levelling compound. Plug any gaps in the edge batten around corners to provide a tanking barrier; this will avoid the self-levelling compound escaping or sinking.

7. Thermostats – Nu-Heat supplies a wide range of thermostats with differing levels of complexity, therefore it is important that the homeowner chooses a model to suit their lifestyle and its operation is fully explained. The choice will affect the first-fix wiring.

8. Sensitive floor finishes – Advise Nu-Heat of any temperature-sensitive floor finishes, e.g. vinyl or engineered timber, as we will supply room thermostats that will control both the room temperature and limit the maximum floor temperature at no extra cost.

9. System programming – The LoPro10™ underfloor heating system should be run in a similar heating pattern as a traditional radiator system, with ON/OFF periods to suit the homeowner’s lifestyle. There is likely to be some fine-tuning required to align the system to the exact heat-loss characteristics of the building. This method of control is the most efficient for this floor construction in a renovation project.

10. Towel-rails – Building Regulations state that heated towel-rails should be fitted in bathrooms and en-suites, as they will support the overall heat output in the room during the winter months. They should provide a minimum of 400watts (depending on the size of the room). Towel-rails can be run traditionally as part of the heating system or alternatively oil filled electric models can be fitted.